JPH0346653B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention includes an exhaust turbo supercharger for supercharging intake air, and the diameter of the exhaust gas introduction passage to the turbine of the exhaust turbo supercharger is This invention relates to an engine equipped with a diameter variable means that varies the diameter according to engine operating conditions.

[Prior art] Conventionally, the diameter of the exhaust passage upstream of the turbine is switched between large and small depending on engine operating conditions such as engine speed and load, and when the engine is operating at low speed, the passage diameter is set to the "small" side. and set it to
Turbine supercharging improves the engine's output performance in the low speed range by narrowing down the exhaust gas and increasing the speed at which the exhaust flows into the turbine, causing the turbine to rotate at high speed to quickly increase boost pressure. The attached engine is publicly known (utility development 1986-
(Refer to Publication No. 161139).

In an engine having such a structure, the turbocharging efficiency can be improved by improving the turbine output in a low speed range, and accordingly, the output performance of the engine can be improved to some extent.

However, in a low speed range, the diameter of the exhaust gas introduction passage is narrowed down to a small diameter, so as the engine speed increases, the exhaust pressure on the upstream side of the turbine increases rapidly. Such an increase in exhaust pressure becomes a major factor that inhibits engine combustibility, such as an increase in the amount of internal EGR (the amount of exhaust gas that remains in the combustion chamber).

Moreover, narrowing down the diameter of the exhaust gas introduction passage as described above causes an extreme drop in exhaust gas temperature. In other words, if the exhaust gas flow rate increases by narrowing the passage diameter, the turbine output will certainly improve, but on the other hand, if the exhaust gas flow rate increases,
Thermal energy contained in the exhaust gas is converted into operating energy and absorbed by the turbine, reducing the exhaust gas temperature by that amount. It is preferable to avoid this decrease as much as possible from the viewpoint of exhaust gas purification.

In particular, during low-speed, low-load steady operation of an engine that does not require high output, if the diameter of the exhaust gas introduction passage to the turbine is narrowed, internal EGR will increase as the exhaust pressure increases, causing excessive engine combustibility. In addition, the exhaust gas temperature decreases, and in order to ensure combustibility, it becomes necessary to increase the amount of fuel, which causes problems such as deterioration of fuel efficiency.

On the other hand, Japanese Patent Application Laid-Open No. 58-176417 discloses that the turbine nozzle area is made variable, and the turbine nozzle area is narrowed in the low rotation range and widened in the high rotation range, and that An engine with a turbocharger has been proposed that controls the throttle according to characteristics that widen in the low load range.

Although this type allows fine control of the turbine nozzle area according to the rotation speed and load, the control becomes complicated and the turbine nozzle area is set small in the low speed range, so the turbine nozzle area is divided into two stages, large and small. There are basically the same problems as in the conventional example of switching. In other words, the method of controlling the turbine nozzle area in proportion to the exhaust gas flow rate seems to be extremely rational at first glance, but as mentioned above,
The problem of reducing exhaust gas temperature is an important factor when considering control.

In addition, when transitioning from medium-speed load to acceleration (high-load) operation, the turbine nozzle area becomes considerably wider in the medium-speed and low-load range, so high output from the turbocharger cannot be expected. However, there is a problem in that acceleration responsiveness cannot be effectively ensured in the initial stage of acceleration.

[Object of the Invention] An object of the present invention is to adjust the diameter of the turbine nozzle of the engine without complicating control in a turbocharged engine equipped with a means for varying the diameter of the exhaust gas introduction passage to the turbine. An object of the present invention is to provide a control device for a turbocharged engine that can perform optimal control according to various operating regions.

[Configuration of the Invention] Therefore, the present invention includes an exhaust turbo supercharger for supercharging intake air, and also adjusts the diameter of the exhaust gas introduction passage to the turbine of the exhaust turbo supercharger depending on the engine operating state. In an engine equipped with a diameter variable means that makes the diameter variable, the diameter of the exhaust gas introduction passage is increased by the diameter variable means in the low speed/low load operating range and in the high speed/high load operating range, while The present invention provides a control device for an engine equipped with an exhaust turbo superintake, characterized in that the diameter of the exhaust gas introduction passage is reduced by the diameter variable means in the operating range of the invention, regardless of the magnitude of the load. .

[Effects of the Invention] According to the present invention, the exhaust pressure can be maintained at a relatively low pressure during low speed and low load operation of the engine, that is, during light load operation, improving combustibility and fuel efficiency. This makes it possible to effectively prevent a drop in the temperature of the exhaust gas, thereby significantly improving the emission performance.

In addition, in the medium-speed operating range, by narrowing the diameter of the exhaust gas introduction passage and increasing supersuction pressure, it is possible to guarantee high engine output, and in particular, it improves acceleration response in acceleration from medium-speed and low load. I can do it.

[Examples] Examples of the present invention will be described in detail below.

As shown in FIG. 1, the engine 1 includes a turbo supercharger 7 installed across an intake passage and an exhaust passage 6, which are opened and closed with respect to a combustion chamber 4 by an intake valve 2 and an exhaust valve 3, respectively. When the turbine 9 is driven by the exhaust gas flowing down the exhaust passage 6, the blower 10 is driven in conjunction with this, and the intake air pressurized by the blower 10 is supplied to the combustion chamber 4. In particular, it has a basic structure that performs so-called intake supercharging.

An air cleaner 11 is installed in the intake passage 5 on the upstream side of the blower 10, and an air flow meter 12 is installed downstream of the air cleaner 11 to measure the amount of intake air from moment to moment. In addition, the blower 10 of the intake passage 5
A throttle valve 13, which is opened and closed according to the load of the engine 1, is provided downstream of the throttle valve 13, and a fuel injection valve 14 is provided downstream of the throttle valve 13.

On the other hand, the exhaust passage 6 is partitioned into a low-speed exhaust gas introduction passage 16 and a high-speed exhaust gas introduction passage 17 by a partition wall 15 at the exhaust gas introduction port of the turbine 9. The upstream side of the valve 17 is opened and closed on and off by a switching valve 18, which serves as a diameter variable means according to the present invention. Furthermore, a catalytic exhaust gas purification device 19 is interposed in the exhaust passage 6 downstream of the turbine 9.

The low-speed exhaust gas introduction passage 16 includes an exhaust passage 6 downstream of the turbine 9 that bypasses the turbine 9.
A waste gate passage 20 is opened to bypass a part of the exhaust gas, and by opening and closing the passage 20 with a waste gate valve 21, the supercharging pressure is set in advance as described below. Control the boost pressure so that it does not exceed the maximum boost pressure.

In addition, the turbine 9 and the catalytic exhaust gas purification device 1
9 and the intake passage 5 downstream of the throttle valve 13 are referred to as exhaust gas recirculation passages (hereinafter simply referred to as exhaust gas recirculation passages).
It's called the EGR passage. )22, EGR
When the exhaust gas recirculation control valve (hereinafter referred to as EGR valve) 23 installed in the passage 22 is opened, part of the exhaust gas is recirculated to the intake side, and as is well known, an inert recirculation is performed. The generation of NOx is suppressed by controlling an excessive increase in the maximum combustion temperature of the engine 1 by exhaust gas.

Those directly or indirectly involved in the combustibility of the engine 1, such as the waist valve 21, the switching valve 18, the spark plug 24 installed in the combustion chamber 4, and the fuel injection valve 14, are detailed below.
Control is performed by a computer 25 installed in the vehicle.

This computer 25 is connected to the air flow meter 1.
2 detected by the intake air amount and rotation speed sensor 26
The engine speed is detected by the pressure sensor 2 installed in the intake passage 5 downstream of the throttle valve 13.
7 and the exhaust pressure detected by the pressure sensor 28 installed in the exhaust passage 6 downstream of the turbine 9 are used as basic data to control the opening and closing of the switching valve 18 as well as fuel injection. It executes fuel control for the valve 14, ignition advance control for the spark plug 24, etc.

The switching valve 18 is basically opened and closed by a diaphragm type switching actuator 29 whose operating source is exhaust pressure in the upstream portion of the turbine in the exhaust passage 6 in which the switching valve 18 is installed.

A first control valve 31 whose opening/closing is controlled by the computer 25 is interposed in the middle of the exhaust pressure introduction passage 30 that introduces exhaust pressure to the switching actuator 29. 31 is opened and exhaust pressure acts on the first pressure chamber 29a of the switching actuator 29, the diaphragm 29b
The actuating rod 29c, one end of which is fixed to the coil spring 29d, is pushed in the direction of arrow A in the figure against the spring force of the coil spring 29d, and the switching valve 18 is opened via the link mechanism 29e. Further, a negative pressure introduction passage 32 having a negative pressure outlet in the intake passage 5 of the throttle valve 13 is communicated with the second pressure chamber 29f of the switching actuator 29. A second control valve 33 whose opening and closing are controlled by is provided. This negative pressure introduction passage 32 and the second control valve 33
As will be described in detail below, when the exhaust pressure is not high enough to open the switching actuator 29, such as when the engine is operating at low speed and low load, the intake air downstream of the throttle valve 13 is This is to ensure that the switching actuator 29 is opened by introducing negative pressure into the second pressure chamber 29f.

Note that the wastegate valve 21 is opened and closed by a diaphragm type wastegate actuator 34 which uses the discharge pressure of the blower 10 as a driving source, and a pressure introduction passage 35 leads the discharge pressure to the wastegate actuator 34. A relief passage 36 communicating with the intake passage 5 upstream of the blower 10 is provided in the middle of the
A control valve 37 for controlling the amount of relief is interposed in the middle. This control valve 37 is controlled by the computer 25, and when the exhaust pressure detected by the pressure sensor 28 installed in the exhaust passage 6 is about to rise beyond a set value, the control valve 37 is controlled by the computer 25. The closing operation closes the relief passage 36, and the pressure introduction passage 3
5, the discharge pressure of the blower 10 is applied to open the waste gate valve 21, and a part of the exhaust gas is passed through the waste gate passage 20 to the turbine 9.
bypass and prevent excessive increase in boost pressure.

Next, a control method for the switching valve 18, which is a feature of the present invention, will be explained.

As shown in FIG. 2, the entire operating range of the engine 1 is divided into a total of three operating zones A, B, and C, and the opening and closing of the switching valve 18 is controlled for each operating zone as follows.

() Low speed/low load operation zone A In this low speed/low load operation zone A, the engine speed detected by the rotation speed sensor 26 is equal to or lower than the set rotation speed, and the engine speed is detected by the pressure sensor 27. In the operating range where the load is below the set value, the computer 25 simultaneously opens the first and second control valves 31 and 33. Therefore, in this case, exhaust pressure acts on the first pressure chamber 29a of the switching actuator 29, and high intake negative pressure downstream of the throttle valve 13 acts on the second pressure chamber 29f, so that both pressure chambers 29a, The differential pressure between 29f becomes large and the switching actuator 29 is reliably opened. For this reason, the switching valve 18
opens the high-speed exhaust gas introduction passage 17, and the exhaust gas flows through both the low-speed and high-speed exhaust gas introduction passages 1.
6 and 17 into the turbine 9. In other words, the passage diameter (A/R) of the entire exhaust gas introduction passage is set to be enlarged. As a result, the exhaust pressure upstream of the turbine 9 is maintained at a relatively low pressure, the decrease in combustibility caused by the increase in the exhaust pressure is compensated for, and the exhaust gas temperature does not drop extremely and the emission performance deteriorates. In other words, in this operating zone A, very high output performance is not required, so flammability,
Control is performed with emphasis on fuel efficiency.

() Intermediate operation zone B In this operation zone B, that is, the operation zone where the amount of exhaust gas is relatively small, excluding the low speed/low load operation zone A and the high speed/high load operation zone C among all operation areas, switching is not possible. Valve 18 is closed.
Therefore, the computer 25 closes both the first and second control valves 31 and 33. Therefore, in this case, the switching actuator 29 functions to close the switching valve 18 by the spring force of the coil spring 29d, thereby closing the high-speed exhaust gas introduction passage 17. As a result, the exhaust gas is introduced into the turbine 9 exclusively through the low-speed exhaust gas introduction passage 16, and the exhaust gas is narrowed down by the low-speed exhaust gas introduction passage 16 and flows into the turbine 9 at high speed. , the turbine 9 is driven at high speed, the blower 10 effectively boosts the pressure of the intake air,
Intake supercharging in this operation zone B is assumed to be effective.

Therefore, in this operation zone B, the necessary high output can be obtained. In particular, in the engine's medium-speed operating range, the exhaust gas introduction passage is narrowed to ensure high output regardless of the load, so even when accelerating from a medium-speed and low load, the engine output rises smoothly. , good acceleration response can be obtained.

In addition, in this operation zone B, the amount of exhaust gas is increased as a whole compared to low speed/low load operation zone A, and the decrease in exhaust gas temperature does not significantly deteriorate the purification performance of the exhaust gas purification device. do not have.

() High-speed/high-load operation zone C In this operation zone C, the switching valve 18 is opened in order to improve the output performance by supercharging, which is the original purpose of the turbocharger 7. In this case, since the exhaust pressure upstream of the turbine 9 is sufficiently high, if the first control valve 31 is opened by the computer 25, the switching actuator 29 can be opened simply by opening the first control valve 31 using the computer 25. Accordingly, the high-speed exhaust gas introduction passage 17
is opened, a large amount of exhaust gas is introduced into the turbine 9 from both the low-speed and high-speed exhaust gas introduction passages 16 and 17, and the turbine 9 and therefore the blower 10 are driven at high speed. As a result, the output of the engine 1 is increased in accordance with the increase in charging efficiency due to supercharging, and high output is achieved.

Note that the boost pressure is controlled through the control of the waste gate valve 21 described above so as not to rise above a preset maximum boost pressure.

In the above embodiment, the exhaust gas introduction passage to the turbine 9 is divided into two exhaust gas introduction passages 16 and 17 for low speed and high speed, and the high speed exhaust gas introduction passage 17 is controlled by the switching valve 18. Although the passage diameter is changed by opening and closing, the present invention provides a low-speed turbo supercharger having a relatively small-diameter exhaust gas introduction passage and a high-speed turbo supercharger having a relatively large-diameter exhaust gas introduction passage. A type of engine equipped with a turbo supercharger, in which the low speed turbo supercharger is used exclusively at low speeds, and the high speed turbo supercharger is dedicated or both turbo superchargers are used at high speeds. Needless to say, it can also be applied to

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram of an engine according to an embodiment of the present invention, and FIG. 2 is a graph showing an example of a switching valve opening/closing control method. 1... Engine, 5... Intake passage, 6... Exhaust passage, 7... Turbo supercharger, 9... Turbine, 1
0... Blower, 14... Fuel injection valve, 16, 17
...Exhaust gas introduction passage for low speed and high speed, 18...
Switching valve, 25... Computer, 29... Switching actuator, 31... First control valve, 32... Negative pressure introduction passage, 33... Second control valve.

Claims (1)

[Scope of Claims] 1. A variable diameter system that includes an exhaust turbo supercharger for supercharging intake air, and that changes the diameter of the exhaust gas introduction passage of the turbine of the exhaust turbo supercharger according to engine operating conditions. In the engine provided with the means, the diameter of the exhaust gas introduction passage is increased by the diameter variable means in the low speed/low load operating range and the high speed/high load operating range, while in the operating range other than the above two operating ranges, A control device for an engine equipped with an exhaust turbo supercharger, characterized in that the diameter of the exhaust gas introduction passage is reduced by the diameter variable means regardless of the magnitude of the load.